It is previously known in the raising and marketing of hogs that it is necessary to separate the hogs when they reach a predetermined market weight for transportation to market. For this reason a number of manufacturers have designed sorters which cause the hogs to pass through one at a time for weighing on a scale within the hog sorter which then activates a gate to select a path for the hog either to a market pen or to a retaining pen depending upon the weight of the hog.
A number of different designs of sorters of this type are readily available. Some utilize a system in which the hogs pass through on a periodic basis, generally to a feeding station. Others use other systems where the hog may be required to backup out of the containment cage or pen into which the hog enters for the weighing action.
In the scale, commonly the hog is marked with a paint marker so as to identify those hogs which weigh within a required range.
Currently sorters are used mostly in food court systems where the hogs have to go through to get feed and in other cases you chase the pigs through every so often to weight and sort them.
One arrangement of this type is shown in U.S. Pat. No. 6,837,189 (Schick) issued Jan. 4, 2005. This provides an arrangement in which animals are sorted between light and heavy into two separate pens using a sorting scale.
Also published International application WO03/103380 (Thibault) assigned to Osborne Industries Inc. and published Dec. 18, 2003 discloses a system of dividing animals into heavy weight pen and a lightweight pen using a sorting scale.
Arrangements of this type are suitable where the barn can be divided into pens of sufficient size that the food courts system is viable.
There are however currently thousands of barns in operation that have between 25 and 45 pigs per pen and can not easily be converted to food court systems or large group pens for automatic weighing and sorting. In those barns operators often use a stationary sorter and bring the pigs out of the pen to the sorter and then return at least all the light pigs back to their pen. This is both labour intensive and hard on the pigs because of the length of the barns.
It is known to move a simple weigh scale from pen to pen since the scale itself is relatively small. This however requires manual management of the animals to direct them into and away form the scale after the weighing is complete which is highly labor intensive.
A sorter of the type with which the present invention is concerned is shown in published Canadian Application No. 2,512,162 filed Dec. 16, 2004 and entitled APPARATUS FOR APPLYING A TATTOO TO A HOG PRIOR TO MARKET and assigned to the present Assignees. The disclosure of this application is incorporated herein by reference for any details of the sorter which may be omitted from this application.
A portable hydraulic livestock scale is shown in U.S. Pat. No. 3,774,704 (Purcell) issued Nov. 27, 1973 which is collapsible by removing certain components such as ramp pieces.
In U.S. Pat. No. 4,905,780 (Goff) issued Mar. 6, 1990 is shown a livestock scale mounted on a large trailer so that the scale can be moved from site to site. However it is clear that this trailer is not designed for movement within the narrow confines of a barn.
In U.S. Pat. No. 4,569,408 (Berns) issued Feb. 11, 1986 is shown a livestock scale where the scale itself is mounted on wheels for transportation within a barn. However this scale does not include any sorting arrangement and is primarily designed for use with piglets in a basket.